Integrated circuits, such as large scale integrated circuits and very large scale integrated circuits typically are tested under various conditions prior to the marketing and incorporating of such circuits into expensive electronic systems. To accomplish the testing, the integrated circuit device under test (DUT) is mounted on a circuit board, which in turn is mounted on and electrically interconnected with a product load board connected to a tester. Signals from the tester are applied through the load board to the circuit board on which the DUT is located to operate the DUT for the purpose of determining whether the various circuits of the DUT are functioning properly.
For some integrated circuit devices, the operating environment in which the device ultimately will be used may be subject to extreme temperatures, either very hot or very cold. Some fabrication defects or operation failures are manifested at only one or both of these extremes; so that it is necessary to test the operation of such devices at the temperature extremes which may be encountered in the subsequent utilization of the devices.
To test integrated circuit devices at cold temperatures, a freezer chamber which has an opening in a side wall with a collar around the opening is employed. The circuit board on which the DUT is mounted is firmly placed against the collar of the freezer to place the DUT in the interior freezer environment. The temperature of such a freezer for cold testing of integrated circuit devices may be -40.degree. C. to -57.degree. C. The opposite side of the circuit board on which the DUT is mounted, as well as the load board and the rest of the test apparatus, is located outside the freezer chamber, and, consequently, is exposed to significantly higher ambient temperatures. The interface between the below freezing temperatures applied to the DUT on the circuit board and ambient room temperatures on the other side of the circuit board frequently causes moisture condensation on the circuit board, as a result of the humidity in the ambient air in the test room. Obviously, moisture buildup can cause device test failures, since the moisture creates short circuits in the various circuit interconnections on the circuit board and between the circuit board and the load board of the test apparatus.
In the past, efforts have been made to direct a drying purge of nitrogen or other suitable gas through the inner ring or central opening of the load board onto the circuit board on which the DUT is mounted. Typically, a hose from a suitable utility monument for supplying the nitrogen purge is held in place in the test head by a foam wadding, with the expectation that the nitrogen then will pass through the test head, the ring or central opening in the load board, and from there onto the circuit board. If the hose is not accurately positioned in the center of the test head, however, the purge gases may be unequally applied to the circuit board of the DUT, and result in only drying of a part of the circuit board. Thus, device test failures and down time still are incurred. Even for a set up which operates acceptably for a period of time, misalignment through jarring of the hose carrying the purge gases or other parts of the apparatus, subsequently may lead to failure of a complete purge of the circuit board.
It is desirable to provide a purge director apparatus which directs the purge gases through the load board in an efficient and controlled manner to overcome the disadvantages of the prior art.